Heated Oxygen Sensor Control Test: Before Convertor

Special Tools, Testers And Auxiliary Items
- VAG 1551/1552 scan tool with VAG 1551/3 adapter cable
- VAG 1598/i8testbox
- Multimeter (Fluke 83 or equivalent)
- Connector test kit VW 1594
- Wiring diagram

Test Conditions
- Coolant temperature at least 80°C (176°F)

Functional Check
- Engine running at idle
- Connect VAG 1551/1552 scan tool and select "Engine Electronics" address word 01.

Indicated On Display

Rapid data transfer HELP
Select function XX

- Press buttons -0- and -8- to select "Read Measuring Value Block" function 08 and press -Q- button to confirm input.

Indicated On Display

Read Measuring Value Block HELP
Input display group number XXX

- Press buttons -0-, -2- and -5- to input display group 025 and press -Q- button to confirm input.

Indicated on display (14 = Display fields).

Read Measuring Value Block 25-->
1 2 3 4

- Check the specifications for O2S control (before three way
catalytic converter) (display fields 1-3).




Display Group 025: Oxygen Sensor Control Before Convertor

Continuation
- If the specification in display field 1 is not attained, or the value does not fluctuate at least 2%:
- Carry out a test drive to remove possible residue on HO2S and repeat check.
- If the the specification in display field 1 is not attained even after a road test, or the value does not fluctuate at least 2%:
- Check O2S heating wiring procedures, listed below.

If the value displayed in display field 1 remains constant:
- Press -C- button.
- Press buttons -1-, -1- and -5- to input display group 115 and press -Q- button to confirm input.

Indicated on display (1-4 Display fields)

Read Measuring Value Block 115-->
1 2 3 4

- Note HO2S voltage in display field 3.




Display Group 115: Heated Oxygen Sensor Before Convertor

- Press -> button.
- Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
- Switch ignition off.




Evaluating display group 025




Evaluating display group 115




Relevance of values in 8-digit number block

Checking Basic Voltage





- Separate 4-pin connector (black) -1- to HO2S -G39- (before three way catalytic converter).





- Connect multimeter with test leads from VW 1594 to measure voltage between terminals 3 and 4 (ECM side of harness connector).
- Start engine and measure the basic voltage.
- Specification: 0.40-0.50 volts

- Switch ignition off.

If the specification is not attained:
- Check HO2S wiring procedures, listed Below.

If the specification is attained:
- Replace HO2S -G39- (before three way catalytic converter).

Checking Heated Oxygen Sensor (HO2S) Wiring.




- Connect VAG 1598/18 test box to ECM wiring harness.




- Separate 4-pin connector -1- (black) to HO2S -G39- (before three way catalytic converter).




- Check wiring between test box and 4-pin connector for open circuit according to wiring diagram (ECM side of harness connector).
- Terminal 3 and test box socket 42
- Terminal 4 and test box socket 20
- Resistance: Maximum 1.5 Ohms

- Additionally, check wiring at 4-pin connector for short circuit to one another.
Terminal 4 and test box socket 42.
- Specification: Infinite Ohms

- Check shielding for short circuit to HO2S wiring according to wiring diagram.
- Terminal 4 and test box socket 56
- Terminal 3 and test box socket 56
- Specification: Infinite ohms

If no wiring malfunction is detected:
- Replace ECM -J220-.
- Read the readiness code, If DTC memory has been erased, repair must be verified via appropriate display group: See Readiness code, creating.